VRayBlend = color + VRayWrapper/Matte + bitmapMask = no go?

[JohnVK]

Hello all,

I have a bit of a problem trying to have a plane act as matte + a masked portion with a material applied to catch shadows while retaining the material (color) portion of the plane to be opaque.

Maybe I'm simply misunderstanding the concept. Either that or I have run into a bug / limitation.


I have set up a simple sample scene and have been trying to figure out why this isn't working. Image 1 is an overview of my shader network. Very simple (or at least, so I thought ;p).

The scene is set up as shown in image 2:

• Box and cylinder have a solid material applied
• Plane has Blend:Matte+color+mask.
• Only a VRaySun for lighting
• VRayCamera
• Image in the environment slot (background) merely to demonstrate the issues

There are several problems (see images 3, 4, 5 and 6):


Image 3: rendered with BF + LC and a VRayBlendMtl

• VRayBlend ignores the mask and/or material (red color) EXCEPT it does take it into consideration for GI as you can see on the shadow side of the cylinder. Pretty much the way it is shown in the preview of the VRayBlend material (can't see the red mat portion in the preview).
• The shadow side of the cylinder becomes semi-transparent, and not just where it is over the plane with the matte applied but over it's total height.
• The cast shadow of the plane with the matte on the box beneath also turns semi-transparent, as does the front side of the box (pretty much anything that's somehow receiving shadow?).
• In the LC calculation the red material IS visible (as shown in image 7) but deleted once BF (or IR) starts calculating!

Image 4: rendered with IR + LC and a VRayBlendMtl
The same as above except that the semi-transparency issue is less obvious.


Image 5: rendered with BF + LC and a Standard Blend material

• Masked portion of the red material is shown this time but everything in the shadows is semi-transparent.
• Edges of the red patch should have a nice soft falloff but instead the edges are very rough / jagged. This is also visible in the shader network material preview of the Standard Blend material.
• The alpha channel also has the rough/jagged edges where the red patch is located.
• Something also looks wrong with the edge of the shadow cast by the cylinder. Edges look sharper on the red patch while the edges outside the red patch look softer
• The cast shadow of the plane with the matte on the box beneath also turns semi-transparent, as does the front side of the box (pretty much anything that's somehow receiving shadow?).

Image 6: rendered with IR + LC and a Standard Blend material
The same as above except that the semi-transparency issue is less obvious.


Basically what I want to achieve is image 5 but with the red color patch to respect the blended falloff of the mask, not the rough/jagged edges and of course without the unwanted transparency in the dark areas. I need (want) this so I can comp a rendered animation over matchmoved footage. I need the matte plane with the partial texture so I can blend this texture into the background while still receiving shadows from the CG objects over it. In as less render passes as possible (tight schedule & small budget!).

Can't this be done with VRay? Do I need to resort to tricks to somehow create my own masks to be able to achieve this? If so, what would be the best and quickest approach?

Thanks in advance for your help!! I'd appreciate it a lot!

Kind regards
John


p.s. images 6 & 7 are in the next post since I can add a maximum of 5 attachments per post.


Edit: forgot to mention the system I'm running this on: 3ds Max 2011 + VRay 1.5SP5

[JohnVK]

Images 6 + 7